Steel reinforcement for reinforced concrete structures



Dec. 15, 1959 w. BOYER ETAL 2,916,910

STEEL REINFORCEMENT FOR REINF ORCED CONCRETE STRUCTURES Filed March 14,1957 'Y ,4 FIGA. F|G,3

INVENTORS WILHELM BOYER KuNo EISENBURGER WALTER HUF GL JOSEF RITTATTORNEY,

United States Patent O ce STEEL REINFORCEMENT FOR REINFORCED CONCRETESTRUCTURES Wilhelm Boyer, Graz, and Kuno Eisenburger, Wels, Austria,Walter Hufnagl, Munich, Germany, and Josef Ritter, Graz, Austria,assignors to EVG Entwicklungsud Verwertungsgesellschaft m.b.H., Graz,Styria,

ustria Application March 14, 1957, Serial No. 645,977

9 Claims. (Cl. 72-l10) The invention relates to steel reinforcements forreinforced concrete structures, and has the main object of providingsteel reinforcements which combine high permissible steel4 stresses withhigh adhesive strength between the steel reinforcements and theconcrete.4

This is a continuation-impart of our application Serial No. 344,082,tiled March 23, 1953, and now. abandoned.

The development of reinforcing rods for reinforced concrete is based onthe desireto apply higher stresses to the steel in the reinforcement andthus to reduce the total amount-of steel in the concrete. Calculationsof the stresses on the rods are valid only if the forces whichcorrespond to the increased stresses in the steel canbe transmitted fromthe steel to .the concrete or vice versa by an improved adherence oranother anchorage of the reinforcing rods in the concrete.` L

The earliest and simplest form of a reinforcing rod for reinforcedconcrete is Va round rod having "a relatively smooth surface. When sucharound Vor sectional rod is used as a reinforcement in concrete, atensile load will cause a transverse contraction of the rod, whichresults in loosening the reinforcement inthe concrete; the remaining`bond between the concrete and "steelis'sucient and pairs of rods whichhave been twisted together have been suggested. Whereas in both casesabetter anchorage is achieved thanwith round rods-and-enablesthepermissible steel stress to be increased to` about 28,000`

p.s.i., the anchorage forces are transmited only by the roughness of thesurface and by the resistance to rotation at the helically twistedcontact surface of the reinforcements. Thus oblique components of forceare set up in the concrete, which can Aproduce wedge eiects resultingYin an unfavorable stress pattern in the concrete.

According to another proposal, a reinforcing rod having grooves in itssides is formed with transverse ribs in the grooves which form anchoringsurfaces extending at right angles to the, rod axis. Whereas thisprovides for a good anchorage in the concrete, which. permits also ofsteel stresses up to 28,000 p.s.i., a further increase of thepermissible steel` stresses is noty possible without. ditlicultybecause, in such reinforcing rods, an unfavorable ratio between thesteel cross-section to the anchoring rib surface area is obtained. Forvarious reasons that ratio can hardly be improved. This is so because anincrease in the rib surface area would involve the danger of a localreduction in quality at the position of the ribs if the reinforcingelements are made of high-grade steel, and because more highlyprotruding ribs would not only be subjected to high bending stresses butwould also render the manipulation and storage of such reinforcing2,916,910 Patented Dec. l5, 1959 correspondingly large amounts ofalloying constituents,A

involving high cost. Y

It is an object of the invention to lprovide a novel reinforcing elementwhich ensures a perfectly safe anchor-A age in the concrete and areliable transmission of forces between the concrete andV steel even ifthe adherence with the concrete is loosened by a transverse contractionunder tensile stress, and which involves no difficultiesl in handlingand can be manufactured with ease, particularly in a high-gradecondition, i.e., with a high yield point, by cold drawing at low cost.

It is another object of the invention to provide welded steelreinforcements which combine a high yield point with good weldingproperties.

It is a further object of the invention to provide strip shapedreinforcement steels which allow comparatively easy shaping by bendingout of the plane of the strip while being comparatively stiff in theplane therof.

I-t is yet another object of the invention to provide reinforcement gridsystems which combine the characteristics of the individualreinforcements referred to hereinabove.

With these and other objects in View we provide a reinforcement steelstrip vfor reinforced concrete structures comprising in combination:longitudinal rods consisting of steel of Va comparatively high yieldpoint arranged parallel to one another, and transverse connectorsinter-` welded with the said longitudinal rods at intervals. For

example the longitudinal rods may consist of a steel having a yieldpoint of more than 70,00 p.s.i. and of a higher content in carbon and/ormanganese than the transverse connectors. The distance between parallellongitudinal rods is of the same order of magnitude as their ownthickness, about equal for rods of 0.8 inch thickness or more, but notless than 0.8 inch forfthinner rods. A spacing of 'about 0.8 inch'and1.2 inches is suitable in most instances. The interval between thetransverse4 connectors is usually of a higher order of magnitude thanthe distance between the longitudinal rods, and does not exceed 8inches. p

The transverse connectors may be pieces of rods or of plates, the lattermay be put edgewise across the longitudinal direction of thelongitudinal rods with their flat faces extending at right angles to thelongitudinal rods.

WhenV such a reinforcing element is embedded in concrete the latter willpenetrate into the spaces between the longitudinal rods and will formbetween the adjacent transverse webs thick bridges on which thetransverse webs are supported. The flat faces of the transverse webs orconnectors prevent a transmission 'of detrimental oblique forces to theconcrete. Then the reinforcing element is subjected to tensile stressonly the adherencebetween the contacting concrete and steel surfaces canbe eliminated whereas the anchorage formed by the transverse webs andconcrete bridges will remain intact. That anchorage is so strong thatany holding head previously required at the ends of the reinforcingelement and pro-V vided mostly by the bending of end hooks can beomitted. As will be explained hereinafter the ratio of the spacingbetween the transverse connectors `or webs to the spacing between thelongitudinal rods must be less than forming in the concrete does notexceed the permissible" maximum value of ym() inch. The optimum valuefor the spacing between the webs depends on the concrete quality, on thepermissible steel stress and on the diam- 3 eter of the longitudinal`rods. If a value smaller than the optimum is chosen a larger amount of-steel is required but the reinforced concrete is not adversely affectedthereby. The thickness of the transverse webs should be in the rangefrom 0.4-0.75 inch.

In order to achieve a perfect welded joint between the longitudinal rodsand transverse webs or connectors the latter should be made of a softersteel than the former. The longitudinal rods may be worked by colddrawing or their high yield point may be due to an appropriatelyhigh-content of alloying constituents such as C and/or Mn. Thetransverse webs should not contain more than a.V relatively smallcontent of said elements.

It has been found that reinforcement strips and-grids according to theinvention allow the use of a steel of a yield-point of about 4000kilograms per square centimeter and of correspondingly high permissibletensile stresses, and at the same time give such an improved adhesivestrength between the steel reinforcements and the concrete that theinavoidable cracks in the concrete do not exceed 0.15 to 0.20 millimeterin width whereby the danger of d'ampness or vapors penetrating right tothe steel reinforcements and causing corrosion isgreatly reduced and thedurability of the reinforced steel construction is improved. Owing tobetter adhesion of the concrete to the steel reinforcements thedistances between adjacent cracks are also reduced. The width of thecracks measured on concrete structures using the reinforcement steelaccording to the invention has proved to be in good agreement withcalculated values. For example, With a steel of a permissible tensilestress of 3000 kilograms per square centimeter and a modulus ofelasticity of 2,100,000 kilograms per square centimeter and a distance100 millimeters between transverse connectors the calculated width ofcracks is =0.14 millimeter for the longitudinal members of thereinforcement stripsl according to the invention.

For a better understanding of the invention, reference may be had to theaccompanying drawings inl which:

Figure 1 of the drawing is a perspective view of a reinforcing elementembodying the present invention;

Figures 2 and 3 respectively are a top plan view and a cross-sectionalview of a reinforcing element;

Figure 4 is a schematic illustration in perspective of a test set up fordetermining the reinforcing strength and the required dimensions of thereinforcing elements according to the invention;

Figure 5 is a cross-section view of the reinforcing element illustratingdimensions on which tests are based;

Figure 6 is a cross-section view of a concrete beam reinforced with areinforcing element of the kind shown in. Figures l and 5;

Figure 7 is a side elevational view of the concrete beam supported atits ends and under load; and

Figure S and Figures 8a, 8b, 8c, and 8d illustrate schematically thestresses on the concrete beam when a crack occurs in the beam.

The reinforcement steel according to Figures l to 3 has a strip-likeshape and consists of two longitudinal rods 11a and 11b which areparallel and are connected with one another by pieces of rod-12 or otherweb forming material lying between them and interwelded with thelongitudinal rods. The transverse webs 12 are spaced from one anotherlengthwise of the rods 11a, 11b a distance s. The longitudinal rods 11a,11b in particular consist of a steel having a high yield point. Thecrosssection of the longitudinal rods 11a, 11b may be round, orprofiled, as the case may be; the cross-section of the oblongcross-section profiles being positioned on edge relative to thelongitudinal dimension of the reinforcement strip, if desired. Thus eachtransverse web may consist of a separate form piece produced e.g., bypressing, stamping or the like.

The interwelded transverse webs 12 form an absolutely rigid connectionbetween the two longitudinal rods 11a, 11b which completely prevents anysliding of the reinforcement relative to the concrete in the zone of thewebs; the anchor resistance can be overcome only by complete destructionof the tension Zone of the concrete. By controlling the spacing betweenthe transverse web 12 the permissible width of cracks can be determined,assuming an appropriate quality of the steel. The spacing between thetransverse webs should be less than 200 millimeters (8 inches).

As regards the spacing a between'the two longitudinal rods 11a and 11b,it should be equal to the diameter or thickness of the rods; with a roddiameter below 20 millimeters the clearance spacing should not be lessthan 20 millimeters (0.8 inch). When two longitudinal rods 11a, 11binterconnected by one or more interwelded transverse webs 12 areembedded in a concrete cube 13, as is shown in Figure 4, and theprotruding longitudinal rods are subjected to tension in the sense ofthe arrow P, the first slight movement of the reinforcing element willoccur with any concrete quality and independently of the diampressure ofthe concrete on the transverse web 12 exceeds the value where fc is theultimate compressive strength of concrete. Said movement can be observedwith a dial gauge 14.

Whenlthe average pressure of the concrete on the transverse web` exceedsthe value the concrete. will be destroyed and the longitudinal rods aswell as theA transverse web will be pulled out ofthe concrete.

Y To 'confirm the dimensions specified for the reinforcing elementsaccording to the invention the cross-section of a reinforcing elementaccording to the invention as shown in Figure 5 will be considered rst.The diameter of the longitudinal rods 11a, 11b is designated ip, thespacing between said rods is designated a. The dimension a is g atthe-SametimeV a sufficiently accurate specification of the length of thetransverse webs 12, which are interwelded to the longitudinal rods 11a,11b. On the one hand the width of the transverse webs should be as largea's possible to ensure that the transverse web provides the largestpossible anchoring surface area for reinforcing'ele- The entire steelcross-section A, of the two longitudinal rods is 2f As-b 2 (4)Therefore:

v F, 2 fyi-fri 5 In the` ensuing explanation, and as used elsewherethroughout this application, have the following meaning:

fc-compressive stress of concrete fc-ultimate compressive strength ofconcrete fet-tensile stress of concrete icy-ultimate tensile strength ofconcrete Figures 6 and 7, respectively, are a cross-sectional view and aside elevation showing a rectangular concrete beam having the width band the height d and reinforced in the tension zone witha reinforcingelement according to the invention. As is apparent from Figure 7 thatbeam is supported at its ends and loaded. An increase inthe load on thebeam will cause a crack to'form in the tension zone, e.g., at the pointx, becausethe tensile stress fet has exceeded the ultimate tensilestrength fet of concrete. At that point x the reinforcement must take upthe entire tensile stress because the locally cracked concrete canV nolonger take up any stress. At the point y, spaced by the distance e fromthe point x no crack has beenformed at that time and high tensilestresses are effective in the concrete so that the reinforcement issubjected only to little stress. In that condition, therefore, thestress distributions fc and ict, respectively, shown below Figure 7 (inFigure 8c for the cracking position x, in Figure 8d for the undamagedposition y) are obtained. The stresses actually taken up by the concreteare shown as hatched areas, while the tensile stress taken up by thereinforcement is shown as a clear area. If the tensile stresses fet inthe concrete exceed the ultimate tensile strength fet the values fc,fc', fat ardifct' also at the point y a second crack will be formed andthe stress distribution shown in Figure 8c in'Figure 7 below point xwill be obtained also at point y as shown in Figure 8d. t

If several transverse webs 12 of the reinforcing element according tothe invention are disposed between the rst cracking point x and thepoint y considered, a stepped stress distribution fs and fet accordingto Figures 8a and 8b will be obtained in the longitudinal rodsV and vinthe concrete before a crack occurs at y. The stepwise stress reductionin the longitudinal rods corresponds to the stepwise increase of thetensile 'stresses in the concrete. The stress steps are disposed at thepositions of the transverse webs, which absorb the stress step withtheir effective web surface areas Fs. Regarding the test resultsexplained with reference to Figure 8 a transverse web having aneffective area Fs can transmit the force F5212 without moving in theconcrete.

If the spacing of the transverse webs is designated s, the number oftransverse webs in the distance e equals The total force which can betransmitted bythe transverse Webs in the distance e without causing amovement of the reinforcement is, therefore,

On the other hand it is apparent from the diagram shown in Figures 8, 8cand 8d that the force required to set up the stress ict in the outermostfiber in tension 1n the tension zone of the beam is determined by fswf..

5ov`-`together with the standarized permissible concrete stress 75 canbe computed'for thesetwo extreme cases.

or, with (5) (If the beam is reinforced with several reinforcingeleirnents, As is to be replaced by 2Aa and Fs by EFS.)

If it is further considered thatthe ratio, fc5/fc amounts for severalconcrete qualities, on an average, to

then the equalization of the Expressions 7 and 8 and the substitution of(9), (10) and solution-for s leads tothe equation s: 96epa #M1-.kl Inorder to obtain an interpretable relation between the parameters s, aand 4:' of the reinforcing element the values e, k and p must bedetermined.l

` The determination -of the distance e between cracks is t `based on therule that cracks in the tension zone of a reinforced concrete structuremust not exceed a width of 1/100 inch but are permissible up to thatharmless width. Because the concrete remains stressless in the tensionzone between two cracks the width of thecrack depends on the elongationof the reinforcing element on the distance e between the two cracks. Ifthe steel stress is designated with fs and the modulus of elasticity isdesignated with Es an elongation of the reinforcing element by 1,myincht will be obtained at For the determination-of the value k the extremecases of `concrete quality in reinforced concrete structures may beconsidered, i.e., the lowest quality fmm` '1800 p.s.i.

f lnm =800 p.s.i., and the highest concrete quality at presentachievable, fcmax =6500 p.s.i. and fc max =3000 p.s.i. The value k iscalculated according to the known equals the relation between the moduliof elasticity of steel and concrete; for the poorest concrete consideredholds n=15, for the best concrete n may be considered as equalling 6.

If the stated Values of fc and n arel substituted in (14) and the steelstress is assumed according to the invention at its lower limitf,=35,000 p.s.i. but at its upper limit in conjunction with the highestconcrete quality as s:50,000 p.s.i., a mean k value of l v k-og3effi-Ima?V (15) the outermost `ber in tensionA accord- .Areinforcedconcrete'bearnl is .correctly reinforced if the tensile force T in thereinforcement is as: great'as vthe highest-permissible compressivefforceC in the concrete.

The tensile force inthe reinforcementequals According to Figure 8 thecompressive force in the concrete equals l 0.16.1010 s 0.6.10*o

effa agi-?? '(20) and, for arm-1&- inch:

giml'iom 21) Frtliermore, if the limits of are calculated for thepoorest and best concrete and steel qualities assumed, (19) gives with asmall margin of tolerance The lower limit for .al d

applies to relatively poor 'qualitiesv of the materials,fthe upper limtfor the best qualities.

The spacing a of the longitudinal rods should be small to--enable thereinforcing element according to the invention to be handled like arod-shaped reinforcing element according to Figures 1 to 4. According toUnited States Standards it must not be less than 1 inch to ensure a safepenetration even of coarse concrete into the space between thelongitudinal rods.

For the dimension a=1 inch, Equation 22 shows that Thus the spacing ofthe transverse webs for 1/2Y inch should ybebetween 2.6:inches and 4.8inches, depending on'. the concreteiquality. `AIn this connection, careis to be taken .above all toremain `.below the upper limit of 8 inchesfor s because tlie width of cracks in the concrete would be increasedif.that limitis exceeded. A value below the lower limit is not criticalbecause it will lead only to a somewhat increasedconsumption Aof webmaterialV but has" .no detrimental consequences f forl the-'reinforcedconcrete structure.

The thickness i of the transverse Webs should be such that the sectionmodulus of said webs at the Welded joint should be capable of aborbingthe fixed-end moment of the transverse Webs, which are considered beamsgripped between the longitudinal rods, at the load obtained under thecalclulated stress condition, taking into account the yield point ofabout 30,000 p.s.i. of the steel used for the web. Since the staticconsideration of this problem involves great difficulty the tolerancesfor the thickness of the web have been determined experimentally. It wasfound that the thickness i of the web should meet the relation Comparedtovknown reinforcements for concrete the reinforcing element accordingto the invention enables a reduction of'steel in the range of LlO-65%,with much reduced transport and handling costs.

The derivation of Formula 19 has been based on the assumption that thetensile force in the reinforcement of the reinforced concrete beam s toequal the maximum permissible tensile strength in the concrete. Thatrequirement is not always fulfilled. There are many cases where theconcrete is not loaded to its full carrying capacity. Owing to thevunderload on the concrete a smaller steel cross-section is required insuch cases. Also'in that case, howeverfthe reinforcement should bedesigned so that the permissible width of crack will not be exceeded.

In order to observe the permissible width of crack on which Formula 16is based even under the changed load and reinforcement conditions thetotal of the effective web areas, represented as the product of theindividual web areas and theV number of Webs on a predetermined distancemust be the same as under the optimum load conditions. This can beachieved by providing a graded series of reinforcing elements accordingto the invention, having different longitudinal rod diameters, anddesigning the distance of transverse webs in that specimen of the serieswhich has the greatest longitudinal rod diameter according' to Formula16; that specimen is usedY for fully utilized concrete; the reinforcingelements of the series having longitudinal rods smaller in diameter havethe same spacing of the transverse-webs as the stronger reinforcingelement designed according to Formula 16 and are used in less highlyloaded concrete.

Equations 7 and 8 state that a certain web area F, is required to obtaina width of crack not exceeding to M00 inch. A reduction of the steelcross-section involves also a reduction in the web area whereas Equa-.tion 5 shows the ratio Fs As to increase with a decrease in thelongitudinal rod diameter. This enables the total web area required tobe ensured by maintaining the web spacing s constant when thelongitudinal rod diameter is decreased.

If the concrete cross-section is fully utilized a longitudinal roddiameter of =1/2 inch, c g., involves a ret quired transverse web areaFs to produce a crack not exceeding JA00 inch in width. If the concretecrosssection is utilized only by half so that only half the steelcross-section is required the use of two reinforcing elements having alongitudinal rod diameter of 1A inch will reduce the steel cross-sectionby half whereas the total transverse Web area'required according toFormula 5 for a web spacing calculated according. to Equat1on 19 for95:1/2 is retained.

The 'new'reinforceme'nt steel maybe bent into the form of linesdesiredirnore easily-than the profile steels of round or squarecross-section because it has a flat shape, and it `hasinoreover theadvantage ascompared with the known'cold-worked reinforcement steelswhich have been preferred because of their higher yield point values,that init a high yield point for the purpose of attaining higherpermissible steel stresses appears combined with the advantage ofbetteradhesive strength. This adhesive strength makes it for examplepossible to dispense with the turning up of end hooks for the purpose ofanchorage. Itis likewise possible to dispense with an anchorage in Vthecompression zonewhich is indispensible with all known profile steels,and tests have proved that the profile steel according to the inventionneed not extend beyond the end point according to calculation. A furtherparticularly valuable advantage arises from the use of reinforcementsteel according to the invention as a prestressed reinforcement inconcrete constructions. This advantage consists in that owing to therepeated direct anchorage along the entire length of the reinforcementsteel stresses are reliably transmitted between the concrete and thesteel in contradistinction to the smooth drawn prestressed wires wheresuch possibility of transmission does not exist, or as compared with theknown reinforcements consisting of intertwisted wires and spacersarranged between the same at places, where such a possibility oftransmission exists to a small extent only. Accordingly the holder headsrequired with pre-stressed smooth wires can also be dispensed with.

Besidse, at least the longitudinal rods may be subjected at one stage ofthe production process of the reinforcement steel according to theinvention to an improving treatment increasing its strength properties,

. and having a width substantially equal to the diameter of thelongitudinal rods, the ratio of the spacing between the transverse websto the spacing between the longitudinal rods fulfilling the relatione.g., to a thermal treatment such as artificial ageing or patenting Thesame effect can alternatively be attained by the addition of appropriatestrength-increasing alloy elements.

The new reinforcement steel is suitable for reinforced concretestructures of any kind.

We claim:

1. An integral reinforcing construction for reinforced concrete, whichcomprises two longitudinal rods of steel, each of a diameter rangingbetween 0.13 inch as a minimum and 1. 2 inches as a maximum, and havingayield point exceeding 70,000 p.s.i. which extend parallel to each other,0.8 to 1.2 inches apart, and transverse webs of softer steel interweldedat intervals to said longitudinal rods and extending at right angles tothe longitudinal rods and having substantially at side faces extendingat right angles to the longitudinal rods and a width substantially equalto the diameter of the longitudinal rods, the ratio of the spacingbetween the transverse webs to the spacing between the longitudinal rodsbeing less than inches where qa is the diameter of the longitudinal rodsin inches.

2. A reinforcing construction as set forth in claim 1, in which thethickness of the webs is between 0.4 to 0.75 o.

3. A reinforcing construction as set forth in claim 1, in which thelongitudinal rods consist of cold-drawn steel.

4. A reinforcing construction as set forth in claim 1, in which thesteel of the longitudinal rods has a relatively high content of alloyingconstituents selected of the class consisting of carbon and manganeseand the steel of the transverse webs has a relatively low content ofsaid alloying constituents.

5. An integral reinforcing construction for reinforced concrete, whichcomprises two longitudinal rods of steel, each of a diameter rangingbetween 0.13 inch as a minimum and 1.2 inches as a maximum, and having ayield point exceeding 70,000 p.s.i., which extend parallel to each otherwith a spacing of about 0.8 to 1.2 inches and wherein fs is thepermissible steel stress in p.s.i., the diameter of the longitudinalrods, sis the spacing between the transverse webs and a is the spacingbetween said rods. l

6. An integral reinforcing construction for reinforced concrete, whichcomprises two longitudinal rods of steel, each of a diameter rangingbetween 0.13 inch as a minimum and 1.2 inches as a maximum, and having ayield point exceeding 70,000 p.s.i. which extend parallel to each otherabout 0.8 to 1.2.inches apart and transverse webs of softer steelinterwelded at intervals to said longitudinal rods and extending atright angles to the longitudinal rods and having at side faces extendingat' right angles to the longitudinal rods and a width substantiallyequal to the diameter of the longitudinal rods, the ratio of the spacings of the transverse webs to the clearance a between the longitudinalrods fulfilling the relation 0.32.10lo 1.2.1010 aff ff each other with aspacing between them about equal to the diameter of said rods, andtransverse webs of softer steel interwelded at intervals to saidlongitudinal rods and extending at right angles to the longitudinal rodsand having substantially fiat side faces extending at right angles tothe longitudinal rods and a width substantially equal to the diameterofthe longitudinal rods, the spacing of the transverse webs being lessthan about 8 inches.

8. A graded series of reinforcing elements for reinforced concrete, inwhich each element comprises two longitudinal rods of steel, each of adiameter ranging between 0.13 inch as a minimum and 1.2 inches as amaximum, and having a yield point exceeding 70,000 p.s.i., which extendparallel to each other with a spacing between them of about 0.8 to 1.2inches and transverse webs of softer steel interwelded at intervals tosaid longitudinal rods and extending at right angles to the longitudinalrods and having fiat side faces extending at right angles to thelongitudinal rods and a width substantially equal to the diameter of thelongitudinal rods, the element having the longitudinal rods largest indiameter fulfilling the relation wherein s is the spacing'between saidwebs, a is the spacing between said rods, and i is the diameter of saidrod in inches whereas in the elements having longitudinal rods smallerin diameter, the transverse webs have the same spacing as in the elementhaving the longitudinal rods largest in diameter.

9. A graded series of reinforcing elements according to claim 8,characterized in the element having the longit 2181` l 1 tudinal`rdslalrgest in diameter the diametel of the longitudinal rods is1/ziinchand the value Y Stephenson Feb. 16, 1892 Cummings May 12,1914Goeltz May 23', 1933 Causey Apr. 13, 1943 FOREIGN PATENTS France 1 June13, 1925 Australia Apr. 27, 1938

